Scanning in optical systems

ABSTRACT

Examples are disclosed that relate to scanning optical systems. One example provides an optical system comprising an illumination source configured to emit light, a first scanning stage configured to receive the light and to scan the light, and a second scanning stage configured to receive and direct the light from the first scanning stage toward a projected exit pupil.

BACKGROUND

Optical systems may scan light from an illumination source in one or more dimensions to produce a viewable image. Various scanning systems may be used, including but not limited to movable mirrors, prisms, lenses, and diffractive elements.

SUMMARY

Examples are disclosed herein that relate to scanning optical systems. One example provides an optical system comprising an illumination source configured to emit light, a first scanning stage configured to receive the light and to scan the light, and a second scanning stage configured to receive and direct the light from the first scanning stage toward a projected exit pupil.

Another example provides an optical system comprising an illumination source configured to emit light, a scanning electro-optic element configured to receive the light and to scan the light, and a waveguide configured to receive light from the scanning electro-optic element and to direct the light toward an eyebox, the waveguide comprising a pupil replication stage.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example optical system.

FIG. 2 schematically shows an example waveguide-based optical system utilizing a first scanning stage and a second scanning stage.

FIG. 3 schematically shows an example non-waveguide-based optical system utilizing a first scanning stage and a second scanning stage.

FIG. 4 schematically shows another example waveguide-based optical system.

FIG. 5 is a flowchart illustrating an example method of scanning light in an optical system.

FIG. 6 shows a block diagram of an example computing system.

DETAILED DESCRIPTION

Scanning mechanisms in optical systems may utilize mirrors, prisms and other optical components to scan light from a light source to generate images. However, such scanning systems may suffer from a small exit pupil (the area through which imaged light passes to exit the optical system), a small eyebox (the region in space in which the image is viewable), and a limited field-of-view. Further, in such systems, the exit pupil may reside inside or very close to the optics used in the scanning system. Because the light passing through the exit pupil continues to expand as it travels from the exit pupil, a user's eye may need to be positioned inconveniently close to or right up against the scanning optic in order to see the full field of view of the imaged light and to avoid a vignetted or clipped image.

Similarly, a waveguide-based optical system may utilize a scanning system to scan light that is input into the waveguide. Due to the location of the exit pupil within the scanning optic, the waveguide may be positioned very close to or against the scanning optic for efficient coupling of the light into waveguide. Although this may provide a compact configuration, current scanning technologies may not be able to provide a desired range of angles of scanned light or be able to scan light at a sufficient rate for image production. For example, the entrance pupil of a waveguide may be approximately 3 mm in diameter, while a microelectromechanical systems (MEMS) mirror scanning system may produce a beam diameter of approximately 1 mm, thus resulting in a light beam diameter that is very small relative to the entrance pupil of the waveguide.

Accordingly, examples are disclosed herein that relate to scanning systems that may provide for larger beam diameters than provided by MEMS or other scanning systems. Further, the disclosed examples also provide for the projection of an exit pupil, thereby allowing a more comfortable spacing to be achieved between an eye and a scanning optical element. The disclosed examples may be utilized in waveguide-based optical systems as well as non-waveguide-based optical systems. In examples that utilize a waveguide, the waveguide may have a pupil replication stage to replicate and expand the exit pupil.

FIG. 1 shows an example optical system in the form of a head-mounted display device 100 that may utilize scanning of light from a light source for image generation. Head-mounted display device 100 includes a frame 102 in the form of a band wearable around a head of user that supports see-through display componentry positioned near the user's eyes. Head-mounted display device 100 may utilize augmented reality technologies to enable simultaneous viewing of virtual display imagery and a real world background. As such, head-mounted display device 100 is configured to generate virtual images via see-through display 104. See-through display 100 as depicted includes separate right and left eye displays 104R and 104L, which may be wholly or partially transparent. In other examples, a see-through display may have a single display viewable with both eyes. See-through display 104 may take any suitable form, such as a waveguide or prism configured to receive a generated image and direct the image towards a wearer's eye. See-through display device 104 may include any suitable light source for generating images, such as one or more laser diodes. Such light sources may be arranged as point source(s), or as an array.

Head-mounted display device 100 further includes an additional see-through optical component 106, shown in FIG. 1 in the form of a see-through veil positioned between see-through display 104 and the background environment as viewed by a wearer. A controller 108 is operatively coupled to see-through optical component 104 and to other display componentry. Controller 108 includes one or more logic devices and one or more computer memory devices storing instructions executable by the logic device(s) to enact functionalities of the display device. Head-mounted display device 100 may further include various other components, for example a two-dimensional image camera 110 (e.g. a visible light camera and/or infrared camera) and a depth camera 112, as well as other components that are not shown, including but not limited to eye-gaze detection systems (e.g. one or more light sources and eye-facing cameras), speakers, microphones, accelerometers, gyroscopes, magnetometers, temperature sensors, touch sensors, biometric sensors, other image sensors, energy-storage components (e.g. battery), a communication facility, a GPS receiver, etc.

FIG. 2 schematically shows an example scanning optical system 200 suitable for use in head-mounted display device 100. Optical system 200 is configured to utilize a first scanning stage 206 for forming an image for viewing, and a second scanning stage 208 to project an exit pupil of the optical system. Optical system 200 comprises an illumination source 202, such as one or more lasers, configured to emit light of any suitable wavelength or wavelengths. Light from illumination source 202 is directed toward a collimator 204, which collimates the light received from illumination source 202. In other examples, such a collimator may be omitted. Light passing through collimator 204 is received at first scanning stage 206. First scanning stage 206 is configured to scan the light on a pixel-by-pixel, or region-by-region basis along an x and y axis to form an image, depending upon whether the light source is a point source, or a two-dimensional array light source (e.g. a light-modulating or light-emitting panel).

The light scanned by first scanning stage 206 is received at second scanning stage 208. Second scanning stage 208 may scan the light received from first scanning stage 206 toward a projected exit pupil 210, thereby allowing downstream optical elements (e.g. a waveguide or a human eye) to be located a comfortable distance from the first scanning stage and the second scanning stage. In contrast, in systems utilizing a single scanning stage, the exit pupil may be located within the scanning stage. As such, an eye, waveguide or other optical element may need to be placed much closer to the scanning stage to avoid light loss or vignetting. Optical system 200 also includes a controller 211 for controlling the operation of illumination source 202, first scanning stage 206, and second scanning stage 208 to form an image and direct the image toward projected exit pupil 210.

Scanning stages 206, 208 may utilize any suitable scanning mechanism configured to scan the light in one or more dimensions. As one example, either or both of scanning stages 206, 208 may take the form of a rotating prism pair, such as a Risley prism pair, where two wedge-shaped prisms are rotated relative to one another to scan a beam of light in two dimensions. Risley prism pairs may produce a beam diameter that is sufficiently large to feed into the entrance pupil of a waveguide, in contrast to MEMS mirror scanners.

As another example, either or both of scanning stages 206, 208 may utilize electro-optics, such as electrowetting technologies, to perform non-mechanical scanning. As a more specific example, an array of electrowetting microprisms (EMPs) may be fabricated in a silicon-on-oxide substrate, and may be controllable via voltage sources to steer an incoming light beam at an angle. The EMP array may be configured to scan the light in two dimensions. Scanning stages 206, 208 also may utilize electrowetting lens elements. As an example of such a configuration, a scanning stage may utilize a two-dimensional, micro-array of electrowetting lens elements, where each lens element comprises a volume of oil and water with an interface configured to vary in shape in a controllable manner and thus steer light based upon an applied voltage. Thus, each electrowetting lens element in the array may separately deviate light, acting similarly to a Fresnel prism. Further, two electrode pairs normal to one another may be used to control each electro-wetting lens element, thus allowing any given lens element in the micro-array to be controllable to steer light in two dimensions.

As yet another example, either or both of scanning stages 206, 208 may utilize liquid crystal elements. The refractive index of a liquid crystal element may be changed by applying voltage to the element, which allows control of the refraction of light by the element. It will be understood that any other suitable scanning technologies may be utilized, including but not limited to deformable polymers.

Continuing with FIG. 2, waveguide 212 receives light from second scanning stage 208 at an input coupling positioned at or near the projected exit pupil 210. The light is conducted along the waveguide 212 via total internal reflection to an output coupling which, in turn, outputs the light toward an eyebox 214. As light propagates through waveguide 212, a field-of-view of the imaged light may be expanded in two dimensions. In some examples, waveguide 212 may include a pupil replication stage 216. The pupil replication stage 216 may include any suitable optical element(s) configured to replicate and expand the exit pupil, including but not limited to one or more surface relief gratings, Bragg gratings, and/or partially reflecting surfaces. Each time light from the light source interacts with an element in pupil replication stage 216, the element makes a copy of the light beam. In this manner, pupil replication stage 216 may create and overlay multiple copies of the exit pupil on one another, thereby creating a rectangular-shaped, or any other suitably shaped, expanded exit pupil. The output grating also may help to expand the light. This configuration may preserve all angles of light across all fields of view within the waveguide while still increasing the size of the exit pupil, which may ensure uniform illumination of the exit pupil as well as uniform energy across all fields of view. Further, the expanded, rectangular-shaped exit pupil may help to accommodate for differences in interpupillary distances of users.

FIG. 3 schematically shows another example optical system 300 for scanning light from an illumination source 302 to form an image. Optical system 300 likewise projects an exit pupil, but does not utilize a waveguide. Instead, optical system 300 projects an exit pupil to a location a comfortable distance away from scanning optics for a user's eye. Optical system 300 comprises a collimator 304, a first scanning stage 306 for scanning light from the light source across a desired area, and a second scanning stage 308 for projecting an exit pupil, as described above with regard to optical system 200. However, rather than a waveguide, optical system 300 comprises a suitable reflective element, such as a partially reflecting mirror 312, to direct at least a portion of the light toward eye 314. Optical system 300 also includes a controller 316 for controlling the operation of illumination source 302, first scanning stage 306, and second scanning stage 308 to form an image and direct the image toward projected exit pupil 310. The location of the projected exit pupil 310 allows scanning stages 306, 308 to be positioned above and away from the front of the eye 314, which may facilitate viewing of a real world background through the optics, e.g. for augmented reality settings.

FIG. 4 schematically shows another example optical system 400 comprising an illumination source 402, a collimator 404, and a scanning electro-optic element 406 configured to receive and scan the light received from illumination source 402 and collimator 404. Optical system 400 also includes an eye tracking system 408 having one or more light source(s) 410 and a camera 412. Light from light source(s) 410 is collimated by collimator 413 and also scanned by the scanning electro-optic element 406. Optical system 400 further includes a first waveguide 414 and a second waveguide 416. First waveguide 414 is configured to receive imaged light from the illumination source 402 and variable optical element 406 and propagate the light throughout first waveguide 408 to deliver the light to a user's eye 412. Likewise, second waveguide 416 is configured to receive light from one or more light source(s) 410 of the eye tracking system 408 and variable optical element 406, and to propagate the light through second waveguide 416 and deliver the light to eye 412.

Light source(s) 410 may be configured to utilize different wavelengths of light than that utilized by illumination source 402, such as infrared light that is not visible to a user. The light from light source(s) 410 reflects from eye 412 and returns in a reverse direction via second waveguide 416 to pass back through scanning electro-optic element 406 and an imaging lens 417 to an eye tracking camera 418. Eye tracking camera 418 may capture images that can be analyzed to detect glints or reflections off the cornea (or other suitable anatomical structure) arising from the light source 410. In some examples, light from light source(s) 410 may be scanned via scanning electro-optic element 406 to produce glints from multiple directions. For example, a single laser may be used to direct IR light in several different pre-determined directions, instead of using multiple light sources each configured to cause a single glint. In other examples, eye tracking system 408 may utilize any other suitable scanner than variable optical element 406, including but not limited to a prism pair.

Optical system 400 also includes a controller 420 for controlling the operation of illumination source 402, light source(s) 410 and eye tracking camera 418 of eye tracking system 408, and scanning electro-optic element 406. In some examples, controller 420 may be configured to provide foveated display capabilities. More specifically, eye tracking may be used to estimate a location of a user's fovea. Then, higher resolution foveal images may be displayed in the estimated location of the fovea, and lower resolution image may be displayed peripherally. The location at which foveal images are displayed likewise may be updated as the position of the user's eye moves.

FIG. 5 shows an example method 500 for scanning light in an optical system. Method 500 includes, at 502, emitting light via an illumination source, such as one or more lasers. Method 500 further includes, at 504, receiving light at a first scanning stage and scanning the light in one or more dimensions, and at 506, receiving the light at a second scanning stage and directing the light toward a projected exit pupil by scanning with the second scanning stage. The projected exit pupil may be positioned at or adjacent to waveguide such that the light is directed into the waveguide, as indicated at 507, or may be directed toward at an intended position of a user's eye via a reflective element, as indicated at 508. In examples where a waveguide is utilized, the waveguide may propagate the light through a pupil replication stage of the waveguide before emitting the light for viewing. In examples where a waveguide is not utilized, a reflective element may be configured to receive light directly from the scanning stage(s) and direct the light toward the eye, such as a partially reflecting mirror, as described above with regard to FIG. 3.

As mentioned above, eye tracking may be used in combination with scanning to display foveated images. Thus, method 500 may include, at 510, receiving eye tracking data from an eye tracking system, which may enable, at 512, providing higher resolution foveal images and lower resolution peripheral images based upon the eye tracking data.

While described herein in the context of near-eye display systems, the example optical systems and methods disclosed herein may be used in any suitable optical system, such as a rifle scope, telescope, spotting scope, binoculars, and heads-up display.

In some embodiments, the methods and processes described herein may be tied to a computing system of one or more computing devices. In particular, such methods and processes may be implemented as a computer-application program or service, an application-programming interface (API), a library, and/or other computer-program product.

FIG. 6 schematically shows a non-limiting embodiment of a computing system 600 that can enact one or more of the methods and processes described above. Computing system 600 is shown in simplified form. Computing system 600 may take the form of one or more personal computers, server computers, tablet computers, home-entertainment computers, network computing devices, gaming devices, mobile computing devices, mobile communication devices (e.g., smart phone), and/or other computing devices.

Computing system 600 includes a logic subsystem 602 and a storage subsystem 604. Computing system 600 may optionally include a display subsystem 606, input subsystem 608, communication subsystem 610, and/or other components not shown in FIG. 6.

Logic subsystem 602 includes one or more physical devices configured to execute instructions. For example, the logic machine may be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions may be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwise arrive at a desired result.

Logic subsystem 602 may include one or more processors configured to execute software instructions. Additionally or alternatively, logic subsystem 602 may include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. Processors of logic subsystem 602 may be single-core or multi-core, and the instructions executed thereon may be configured for sequential, parallel, and/or distributed processing. Individual components of logic subsystem 602 optionally may be distributed among two or more separate devices, which may be remotely located and/or configured for coordinated processing. Aspects of logic subsystem 602 may be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

Storage subsystem 604 includes one or more physical devices configured to hold instructions executable by logic subsystem 602 to implement the methods and processes described herein. When such methods and processes are implemented, the state of storage subsystem 604 may be transformed—e.g., to hold different data.

Storage subsystem 604 may include removable and/or built-in devices. Storage subsystem 604 may include optical memory (e.g., CD, DVD, HD-DVD, Blu-Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and/or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.), among others. Storage subsystem 604 may include volatile, nonvolatile, dynamic, static, read/write, read-only, random-access, sequential-access, location-addressable, file-addressable, and/or content-addressable devices.

It will be appreciated that storage subsystem 604 includes one or more physical devices. However, aspects of the instructions described herein alternatively may be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.) as opposed to being stored on a storage medium.

Aspects of logic subsystem 602 and storage subsystem 604 may be integrated together into one or more hardware-logic components. Such hardware-logic components may include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC/ASICs), program- and application-specific standard products (PSSP/ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

When included, display subsystem 606 may be used to present a visual representation of data held by storage subsystem 604. This visual representation may take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage machine, and thus transform the state of the storage machine, the state of display subsystem 606 may likewise be transformed to visually represent changes in the underlying data. Display subsystem 606 may include one or more display devices utilizing virtually any type of technology. Such display devices may be combined with logic subsystem 602 and/or storage subsystem 604 in a shared enclosure, or such display devices may be peripheral display devices.

When included, input subsystem 608 may comprise or interface with one or more user-input devices such as a keyboard, mouse, touch screen, or game controller. In some embodiments, the input subsystem may comprise or interface with selected natural user input (NUI) componentry. Such componentry may be integrated or peripheral, and the transduction and/or processing of input actions may be handled on- or off-board. Example NUI componentry may include a microphone for speech and/or voice recognition; an infrared, color, stereoscopic, and/or depth camera for machine vision and/or gesture recognition; a head tracker, eye tracker, accelerometer, and/or gyroscope for motion detection and/or intent recognition, as well as electric-field sensing componentry for assessing brain activity.

When included, communication subsystem 610 may be configured to communicatively couple computing system 600 with one or more other computing devices. Communication subsystem 610 may include wired and/or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem may be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some embodiments, the communication subsystem may allow computing system 600 to send and/or receive messages to and/or from other devices via a network such as the Internet.

Another example provides an optical system, comprising an illumination source configured to emit light, a first scanning stage configured to receive the light and to scan the light, and a second scanning stage configured to receive and direct the light from the first scanning stage toward a projected exit pupil. The one or more of the first scanning stage and the second scanning stage may additionally or alternatively include a Risley prism pair. The one or more of the first scanning stage and the second scanning stage may additionally or alternatively include a scanning electro-optic element. The one or more of the first scanning stage and the second scanning stage may additionally or alternatively include a liquid crystal element. Further, the one or more of the first scanning element and the second scanning element may additionally or alternatively include a plurality of electrowetting lenses. The illumination source may additionally or alternatively include a point source. The illumination source may additionally or alternatively include a two-dimensional array source. The optical system may additionally or alternatively include a waveguide positioned to receive light at the projected exit pupil. The waveguide may additionally or alternatively include a pupil replication stage. The optical system may additionally or alternatively include a partially reflective mirror positioned to receive light from the second scanning element and to redirect at least a portion of the light toward an eyebox. The optical system may additionally or alternatively include a computing device and an eye tracking device, and the computing device may additionally or alternatively be configured to produce higher resolution foveal images and lower resolution peripheral images based upon eye tracking data from the eye tracking device. The eye tracking device may additionally or alternatively include one or more light sources, a camera, and a waveguide may additionally or alternatively be configured to deliver light from the light sources toward an eyebox, and to deliver image data from the eyebox to the camera.

Another example provides a method of operating a display device, the method comprising emitting light via an illumination source, receiving the light at a first scanning stage and scanning the light along at least one dimension, and receiving the light at a second scanning stage and directing the light via the second scanning stage toward a projected exit pupil. In this example, one or more of receiving the light at the first scanning stage and receiving the light at the second scanning stage may additionally or alternatively include receiving the light at a Risley prism pair. Further, one or more of receiving the light at the first scanning stage and receiving the light at the second scanning stage may additionally or alternatively include receiving the light at a scanning electro-optic element. The method may additionally or alternatively include receiving the light at a waveguide and propagating the light through an exit pupil replication stage of the waveguide. The method may additionally or alternatively include receiving eye tracking data from an eye tracking device, and providing higher resolution foveal images and lower resolution peripheral images based upon the eye tracking data.

Another example provides an optical system, comprising an illumination source configured to emit light, a scanning electro-optic element configured to receive the light and to scan the light, and a waveguide configured to receive light from the scanning electro-optic element and to direct the light toward an eyebox, the waveguide comprising a pupil replication stage. Additionally or alternatively, where the scanning electro-optic element is a first scanning stage, the optical system may include a second scanning stage configured to receive the light from the scanning electro-optic element and to direct the light toward a projected exit pupil. The scanning electro-optic element may additionally or alternatively include one or more of an electrowetting element, a liquid crystal element, and a deformable polymer element.

It will be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and/or described may be performed in the sequence illustrated and/or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed.

The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof. 

1. An optical system, comprising: an illumination source configured to emit light; a first scanning stage configured to receive the light and to scan the light; and a second scanning stage configured to receive and direct the light from the first scanning stage toward a projected exit pupil.
 2. The optical system of claim 1, wherein one or more of the first scanning stage and the second scanning stage comprises a Risley prism pair.
 3. The optical system of claim 1, wherein one or more of the first scanning stage and the second scanning stage comprises a scanning electro-optic element.
 4. The optical system of claim 3, wherein one or more of the first scanning stage and the second scanning stage comprises a liquid crystal element.
 5. The optical system of claim 3, wherein one or more of the first scanning element and the second scanning element comprises a plurality of electrowetting lenses.
 6. The optical system of claim 1, wherein the illumination source comprises a point source.
 7. The optical system of claim 1, wherein the illumination source comprises a two-dimensional array source.
 8. The optical system of claim 1, further comprising a waveguide positioned to receive light at the projected exit pupil.
 9. The optical system of claim 8, wherein the waveguide comprises a pupil replication stage.
 10. The optical system of claim 1, further comprising a partially reflective mirror positioned to receive light from the second scanning element and to redirect at least a portion of the light toward an eyebox.
 11. The optical system of claim 1, further comprising a computing device and an eye tracking device, and wherein the computing device is configured to produce higher resolution foveal images and lower resolution peripheral images based upon eye tracking data from the eye tracking device.
 12. The optical system of claim 11, wherein the eye tracking device comprises one or more light sources, a camera, and a waveguide configured to deliver light from the light sources toward an eyebox, and to deliver image data from the eyebox to the camera.
 13. A method of operating a display device, the method comprising: emitting light via an illumination source; receiving the light at a first scanning stage and scanning the light along at least one dimension; and receiving the light at a second scanning stage and directing the light via the second scanning stage toward a projected exit pupil.
 14. The method of claim 13, wherein one or more of receiving the light at the first scanning stage and receiving the light at the second scanning stage comprises receiving the light at a Risley prism pair.
 15. The method of claim 13, wherein one or more of receiving the light at the first scanning stage and receiving the light at the second scanning stage comprises receiving the light at a scanning electro-optic element.
 16. The method of claim 13, further comprising receiving the light at a waveguide and propagating the light through an exit pupil replication stage of the waveguide.
 17. The method of claim 13, further comprising receiving eye tracking data from an eye tracking device, and providing higher resolution foveal images and lower resolution peripheral images based upon the eye tracking data.
 18. An optical system, comprising: an illumination source configured to emit light; a scanning electro-optic element configured to receive the light and to scan the light, and a waveguide configured to receive light from the scanning electro-optic element and to direct the light toward an eyebox, the waveguide comprising a pupil replication stage.
 19. The optical system of claim 18, wherein the scanning electro-optic element is a first scanning stage, further comprising a second scanning stage configured to receive the light from the scanning electro-optic element and to direct the light toward a projected exit pupil.
 20. The optical system of claim 18, wherein the scanning electro-optic element comprises one or more of an electrowetting element, a liquid crystal element, and a deformable polymer element. 